Numerical simulation of flue gas recirculation in a lime rotary kiln

Yu Zhang and Shuman Wang

Energy, 2024, vol. 297, issue C

Abstract: In this paper, numerical simulations of the effects of the primary air and secondary air FGR (Flue Gas Recirculation) ratios in a lime rotary kiln on combustion characteristics, NOx generation, and limestone calcination degree were studied in detail. The results revealed that two distinct temperature peaks were observed along the z-axis of the kiln. Upon the addition of recirculated flue gas to the primary air, the entrainment effect was enhanced, resulting in a shorter flame length, a lower first peak temperature, and a higher second peak temperature. For the secondary air, the two peak temperatures both decreased due to the low inlet temperature. With an FGR ratio of 0.20, the primary air reduced NOx generation by 22.5%, while the secondary air reduced it by 80.5%. However, they also dropped the final limestone calcination degree. Especially secondary air FGR, it decreased the final calcination degree by 5.9%, much higher than 1.6% of the primary air. Hence, primary air FGR is a better option for balancing between NOx emissions and quicklime quality. However, in case of high NOx emissions, it is recommended to choose secondary air FGR and prolong the residence time of limestone in the preheater.

Keywords: Lime rotary kiln; FGR; Combustion characteristics; NOx generation; Limestone calcination degree (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:297:y:2024:i:c:s0360544224008703

DOI: 10.1016/j.energy.2024.131098

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